Quite a while back I had trouble with the Pac Brake sticking on. I followed advice from this forum and put a filter in the vacuum hose, etc., and it was......somewhat better. I left on a long trip about then and 10,000 miles later the Pac Brake was operating like brand new. Must've taken that long to clear all the carbon out, or something, I guess, but it worked fine for about a year.

Lately it's quit coming on at all when I pull the switch, so I just did some trouble shooting. Solenoid works fine and vacuum switches from lower to upper port when switching on and off, but moving the hoses back and forth from vacuum to none only moves the plunger a little bit. Pulling on the plunger yoke with channel locks will only move it half way. Does this mean the vacuum actuator cylinder is worn out ?? I tried lubricating it with no joy. This is a 2002 model. Thanks

Lar.

 

Try disconnecting the cylinder rod from the exhaust valve lever arm. You will then be able to tell if the problem is in the vacuum cylinder or exhaust valve. Mine sticks from time to time and it has always been carbon buildup on the exhaust valve shaft. I work the valve back and forth while spraying penetrant on the shaft until I can get over 90* of rotation.

 

OK, I did as you said, and the plunger works fine. The butterfly (??) was really jammed. I found that a 5/8" socket with a short extension gives enuf leverage to work it back and forth, and I did that for quite a while. It's still a little stiff and squeaks a bit. Sitting at idle it comes on very slowly, and goes off quickly. I'll try driving it soon and see if it loosens up. Thanks

Lar.

 

Lar,

When I first had this problem I pulled the PacBrake and cleaned the crud from around the butterfly thinking that was the problem. What I found was that the pivot shaft was binding in the bore. I don't know if this is caused by soot or corrosion. I freed it up by spraying penetrating oil in the bores while working the lever back and forth. It takes quite a while to loosen it up but when it's free you should be able to get over 90* of rotation.